Took my new to me 92 300SE, 98,000 miles, on our first road trip this weekend. Noticed about 4 to 6 times each way that while the cruise was set at 75MPH, the trans would appear to down shift. No drop in speed, just RPM from around 3,000 to around 4,000. Would stay there for 1 to 3 miles then shift back up with corronsponding drop in rpm. It also did this not on cruise control, not going up hills, not passing, just level smooth driving


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85 300SD
92 300SE

1992 300SE, that would be the 5 speed 722.5 transmission. Always first check the trans. bowden cable, I believe that if you look below the front of the air filter housing you can see a plastic linkage piece that comes to a point, and it should be lined up directly pointing to a plastic 'nub'. It is possible that a very slight incline could be causing your downshift. Anything else and I would have to look it up at work. Does this 'new' car come with any used car warranty?

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I did check the bowden cable, the "points" line up perfect. What next?

The 722.5 had a problem with an electric solenoid that is located inside the valve body. I have replaced several and have fixed the problem.


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Benzmac:
1981 280GE SWB
1987 16V
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